X80钢焊接接头在模拟天然气凝析液中的腐蚀行为

Corrosion Behavior of X80 Steel Welded Joint in Simulated Natural Gas Condensate Solutions

通过正交实验设计、失重实验和电化学实验,研究了HAc、Cl-和乙二醇(MEG)浓度以及温度(T)等因素对X80管线钢在CO2饱和的模拟天然气凝析液中腐蚀行为的影响。结果表明,焊接接头形成宏观腐蚀原电池,腐蚀速率明显大于母材,焊缝区作为阳极区腐蚀加速成为焊接接头的薄弱环节;4种因素对腐蚀过程影响的显著程度依次为:c(HAc)>T?c(Cl-)>c(MEG),c(HAc)与T为影响的主要因子,c(Cl-)与c(MEG)为次要因子。母材和焊缝腐蚀倾向均随着温度的升高而增强;由于Fe(Ac)2作为腐蚀产物保护性较差,随着c(HAc)的升高,母材和焊缝的阻抗降低、腐蚀速率升高。基于正交实验结果,建立了多元线性回归方程。

Carbon steels are widely used as transportation pipelines in oil and gas fields and welding is one of the main ways of connecting pipeline steel.The welded joints are easily corroded due to the difference in composition,structure and properties of the various components.The effect of content of HAc,Cl-,ethylene glycol(MEG)and temperature(T)on the corrosion behavior of welded joint of X80 steel in a simulated natural gas condensate saturated with CO2 was studied by the orthogonal experimental design,weight loss experiment and electrochemical experiment.It is demonstrated that the corrosion rate of the welded joint is significantly higher than that of the base metal because of the formation of macroscopic corrosion galvanic cells,and the corrosion of the weld metal as an anode region is accelerated to become a weak link of the welded joint.The significance of the four factors on the corrosion process is:c(HAc)>T?c(Cl-)>c(MEG),c(HAc)and T are the main factors affecting the corrosion behavior,and c(Cl-)and c(MEG)are secondary factors.Base metal and weld metal corrosion tendencies increase with increasing temperature.Because ferrous acetate is less protective as a corrosion product,as the c(HAc)increases,the impedance of the base metal and weld metal decreases,and the corrosion rate increases.Based on the results of orthogonal experiments,a multivariate linear regression equation was established.